Due to their low ohmic dissipation, superconductors have the potential of many technical applications. Superconductors can be used in resonators, cables, electromagnets, transformers, electric motors and generators. Another technical application is the superconductor based implementation of quantum information devices based on the Josephson effect.
Generally, there is a lot of interest for terahertz frequency oscillators based on superconductor materials. Several terahertz frequency oscillators are known based on the Josephson effect using a Josephson junction. Typically a Josephson junction is made up of two superconductors, separated by a non-superconducting layer which is so thin that electrons can cross the insulating barrier by tunnelling. Some examples of the use of these junctions for terahertz frequency oscillators are described in e.g. European Patent application EP0 372 951, describing a Josephson junction comprising an oxide superconductor thin film, in U.S. patent application U.S. Pat. No. 3,778,893, describing a method for fabricating oscillator by placing a Josephson junction in an external field, and in European Patent application EP0 744 827 A1 describing a method for making a high frequency oscillator by applying a voltage to a Josephson device. However, up to now there has been little progress in the development of superconductors as active elements in e.g. electrical circuits, mainly because the terahertz frequency oscillators based on the Josephson effect have only a weak output power.